carfully bend the tabs inward a small amount, also check and see if the rubber gasket in the cap is shot. Make sure you remove the set screw in the rim of the cap before removal. Don't worry about replacing the set screw, it is a PITA, and it does not need it. New caps are cheep if that don't do it. You may find one that fits at an auto part store. Hoser
(Just a little more polite translation of RJ's post)